Ingot mold



GATHMANN June 13, 1933.

Patented June UNITED .sTA'ri-:s

PATENT. oFl-'lclzl HIL GTEHN, BALTIIOBE, mm

meor nom) Application med January 18, 1983. Serial No. 652,084.

Thisinvention relates to metallic ingot molds, and particularly to molds havm a matrix the horizontal cross section of which will produce inots of a generally rectangular contour A4''with is-cooled very rapidly and crystallizes in the form of dendrites, which grow into the mother liquid at substantially right angles to the mold matrix, while the' remainder of the ingot is composedof free or equiaxed crystallization. The ratio of thedepth of the ingot metal comprising dendritic crystallinestructure to the minimum cross sectional width of the ingot depends upon such factors as the mold tem erature and pouring temperature, the rate of teeming, and the size and contour of the ingot being formed. With proper mold and pouring temperatures and correct teeming, the maxlmum depth of the zone of dendritic crystallization is from one sixth to one fifth of the minimumcross section of the ingot in ordinary killed -steels.

As explained in considerable' detail in my Patent 1,892,56 9, the primary corners of an ingot of the contour described in said patent [break contact with the mold chamber' walls soon. after the formation of the initially solidified, relatively thin ingot skin, due to the differential shrlnkage of the ingot in the mold (i. e., the ot contracting in cross sec-A tion and the mo d expanding in cross section), and the dendritlc or chill crystals do 'not extend as far inwardly at the primary corners of the ingot as they do adj acent'the curved portions of the primary sides of the ingot. Illdacrosc0picstudies of etched cross Sections of ingots of the type shown and described in this patent produced in commercial practice have disclosed that 'at the primary corners of such an ingot thel dendriticcrys- .tals extend inwardly a distance equal to only about one-twentieth of the minimum cross cross sectiona section of the ingot as against one sixth to one fifth at the central portions; and I have found that, for this reason, the radii of the,` `prlmary corners of the ingot need -not Ibe so great as` the radii of the other outwardly .55'

curved portions of the ingot surface. By virtue o this fact, it-is possible to employ aj relatively small curvature atthe primary corners, thus providing a contour adapted',

to most eflicient reheatmg and rolling, and 00' at the same timelocatiilgl the foci of the radii forming the primary corner walls within the,4 zone of free or equiaxed crystals so that there' is little or no danger of the formation of 'so--y called cleavage planes. It is most important that the radii forming the primary corners 4 be not too large 5 otherwise the ingot corners1 may crack vertically during reheating and`` laps and tears may occur during the reduction of the ingot to blooms, slabs, and 80.70

forth. To satisfy the requirements for best' reheating and rolling properties as well as the requirements of crystallization in the ingot necessitates that the curvature of the corners of the solidified ingot .be Controlled rather exactly, this being a basic principle upon which the present invention is founded. y It is well established practice tol make' allowance for shrinkage of an ingot amounting to about one eighth inch per' foot of i'n- 3 got cross section. have discoveredthat, in vorder to produce aneingot ha'vin primary corners described by radii of a pre etermined length relative to the minimum cro's's sectional 1;

\dimension of the ingot, such for example las disclosed inmy Patent 1,892,569, the corner' radii in the metallic mold matrix must be considerably greater than the radii desired in the ingot when it is ready for the reduction process. From tests made, I have found that' 9 a mold provided with .primary corner radii.

vhaving 'a len h of' between one eighth and4 one eighteent' of the minimum cross section of a mold matrix of my contour will produce a solidified ingot having primary,A corner radii... between one tenth and one twentieth of.tl 1 e' minimum cross section of said ingot.

Accordingly, an object of my present., in-h vention isto provide a mold matrix of such contour that the arcs defining the coneave portions ofv the mold matrix at the primary corners will produce ingots substantially within the limits specified in my aforesaid Patent 1,892,569.

The invention may be embodied in any type of vertical mold, having big-end-up, big-end down, or parallel chamber Walls.

In the drawing:

Figure 1 is a longitudinal cross sectional view of a mold having a contour in accordance with the present invention.

Figure2 is a horizontal cross sectionalview taken on lines 2-2 of Figure 1.

Figure 3 is a fragmentar view on an enlarged scale showing graphically in horizontal cross section the relative relation between the radii of the arcs defining the primary corners of a mold matrix and the radii'of the arcs defining the primary corners of a solidified ingot produced therein.

For purpose ofillustration, a mold M of the big-end-up Gathmann type, necked in at the bottom as at 1, is shown in Figure 1.

The preferred contour of the cross section of the mold matrix in accordance with .the present invention is shown in Figures 2 and 3 of the drawing, from which it will be noted' that the horizontal cross section of the mold matrix is o f generally rectangular contour and is defined by four primary sides 2, each side being connected to an adjacent side by outwardly arched primary corners 3 by means.

of secondary corner portions 4 referably gutwardly arched salients 5 flank and merge with and form a part of the primary sides 2 and preferably are subtended by angles a of less than sixty degrees, the foci of the radii 6 formin said salients 5 lying well within the zone o free crystallizatiom The relative extents of the zones of dendritic and 'free or equiaxed crystals forming the ingot structure are shown graphicall as merging one with the other by means o dotted lines X in Figure 3 of the drawing. For the reasons explained in my Patent 1,745,089, of January 28, 1930, it Iis desirable that the primary sides 2 be given an inwardly curved Contour and that these sides be relatively narrow as compared to the cross section of the ingot.

From deduction and tests made and through the observation of the production of many commercial ingots of the type shown in my Patent 1,892,569 before mentioned, I have determined that an in ot of this contour contracts and frees itself om the mold substantially as shown in Figure 3. An annular space or air gap S begins to form soon after the ingot is cast, and is widest at the primary corners 3' of the ingot, resulting, through the formation b free crystalline contraction, in corner radii 7' at the corners of the solidified ingot which are smaller than the radii 7 of the corners 3 of the mold matrix in which the ingot was cast. Figure 3 graphically shows miaaae the decrea'se in length by shrinkage of the' radius 7 forming the corner of the mold matrix and which was momentarily the radius of the in ot corner 3'. As stated, this Shrinkage o the primary corners is materially reater than the wellknown shrinkage in the ody of the ingot. For example, if the horizontal cross section b of the mold matrix is made twenty inches and the primary corners 3 are generated b radii 7 measuring two inches, the ingot I, uring'solidific'ation, will assume at its corners 3' a radii 7' measuring about one and five eighths to one and three quarters inches.

I have found it necessary, therefore, to design and' make the radii 7 definin the primary corners 4 -of the mold matrix fglefinitely larger than that desired in the finished or solidified ready-for-rolling ingot of this type. The radii 7 of the mold corner walls should be between one eighth and one eighteenth of the length of the cross section Z) of the ingot andl preferably about one tenth as long as the cross section b. Thus, in designing a mold in accordance with the present invention, I lay out the walls, exclusive of the corners, to conform substantially to the shape of the ingot to be produced, and lay out the rounded corner walls 3 With radii 7 longer than the corner radii 7' desired in the cast ingot. In other words, in making the mold, the walls thereof exclusive of the corner walls are shaped to conform substantially to the shape of the ingot, Whereas the corner walls of the mold are shaped to radii longer than the predetermined corner radii of the ingot to be produced.

In my beforementioned Patent 1,892,569, I have disclosed and claimed ingots of specific contours having. primary outwardly arched corners, the radii of which have a. length of less than one tenth but greater than one twentieth of the minimum cross sectional dimension of the ingot. According to the present invention, which relates specifically to the cross sectional contourand relative dimensions of the contour of the mold matrix, the radii 7 of said outwardly curved primary corners 3 of the mold matrix are of a length less than one eighth but` greater than one eighteenth of the minimum cross sectional dimension of said mold matrix, and the arcs defining said outwardly curved primary corners 3 are subtended by angles C materially greater than ninety de-` grees but preferably not more than one hundred degrees and in most cases about ninetyfivel degrees. Within the proportional dimensions of the cross section of the mold matrix herein shown and 'described, I am enabled definitely to produce ingots of a cross sectional contour substantially as shown and claimed in my Patent 1,892,569, of December 27, 1932. In producingv ingots according to this invention, I confine portions 'leo ico

of the body of molten metal by mold wall retaining surfaces which, exclusive of the corners, correspond to 'the contour of the ingot to be produced, and confine intervening corner portions of the molten body by arcuate mold Wall retaining surfaces interposed between and connecting said first named surfaces and being of larger radii than the desired predetermined corner radii of the ingot io to be produced.

I claim:

1. A metallic ingot mold having a Vertically extending ingot forming chamber of generally rectangular cross section, having 115 four sides, at least two opposed sides each including an inwardly arched portion and a pair of outwardly arched portions fianking said inwardly arched portion, the radii of said outwardly arched portions being at least one sixth of the minimum cross section4 of the mold matrix and four outwardly arched primary corners respectively intervening between and connecting adj acent sides, the radii of said primary Corners being less than one eighth but greater than one eighteenth of the minimum cross sectional dimension of the mold matrix.

2. A metallic ingot mold having a vertically extending ingot forming Chamber of generally rectangular cross section, the matrix having four sides, at least two opposed sides each including an inwardly arched portion and a pair of outwardly arched portions flanking said inwardly arched portion, the

'35 radi of said outwardly arched portions being at least one sixth of the minimum cross section of the mold matrix, and four outwardly arched primary oorners respectively intervening between and connecting adj acent 40 sides, the radii of said primary corners being less than one eighth but greater than one eighteenth of the"minimum cross sectional dimension of the mold matrix and the arcs defining said primary corners being subtend- 1ed by angles materially greater than ninety degrees.

3. A metallic mold having a Vertically extending ingot formingchamber of generally rectangular cross section defined-by four primary sides, at least two opposed sides each including an inwardly arched portion and a pair of outwardly arched portions flanking said inwardly arched portions, the radii of said outwardly arched portions being at least one sixth of the minimum cross section of the mold Chamber, and four outwardly arched primary corners respectively intervening between and connecting adj acent sides, the radii 'of said primary corners being equal to approximately one tenth of the minimum cross sectional dimension of the mold matrix. In testimony whereof, I have hereunto sub-\ scribed my name. i

"' EMIL GATHMANN. 

